1. Field of Invention
The present invention relates to a control circuit and a control method of a light emitting device circuit; particularly, it relates to such control circuit and control method with a hot swapping protection function.
2. Description of Related Art
FIG. 1 shows a schematic diagram of a prior art light emitting diode (LED) power control circuit 100. As shown in FIG. 1, the LED power control circuit 100 controls an LED circuit 10. The LED power control circuit 100 includes a control circuit 110, a power stage circuit 120, and a current sense circuit 130. The control circuit 110 is connected to the current sense circuit 130 to receive a current feedback signal FB. The control circuit 110 generates a control signal GATE according to the current feedback signal FB, to control a power switch of the power stage circuit 120 accordingly such that an input voltage Vin is converted to an output voltage Vout, and an output current is provided to the LED circuit 10. VCC is a power supply voltage of the control circuit 110, and GND is a ground level of the circuitry. The power stage circuit 120 may be a synchronous or asynchronous buck, boost, inverting, buck-boost, or inverting-boost power stage circuit as shown in FIGS. 2A-2J.
In normal operation, the LED power control circuit 100 regulates the output current at a fixed predetermined current. When the LED circuit 10 is suddenly removed during the normal operation without shutting down the LED power control circuit 100, the control circuit 110 will continue trying to regulate the output current at the fixed determined current, causing not only unnecessary power consumption but also serious danger because the output voltage Vout may rise to a dangerous level. At such dangerous level of the output voltage Vout, if the LED circuit 10 is reconnected to the power stage circuit 120, an instant surge current may be generated, which may damage circuit devices and shorten lifetime of the circuitry.
In view of above, the present invention proposes a control circuit and a control method of a light emitting device circuit with hot swapping protection function (“hot swapping” meaning to remove and/or reconnect an LED circuit while power ON).